1. Field of the Invention
This invention relates to a magnetic disk apparatus and, more specifically, to a magnetic disk apparatus of the type in which head positioning is performed by means of a swing arm and which has an improved joint structure for connecting a head assembly to a head positioning mechanism.
2. Description of the Related Art
In a magnetic disk apparatus of the type in which the head positioning is effected by means of a swing arm assembly, the moment of inertia of the rotating members about the axis of rotation of the swing arm assembly can be reduced to assure that the assembly can be quickly accelerated and decelerated and the head can be reliably set to a desired position on the surface of a rotating disk. This leads to a reduction in power consumption, thereby making it possible to realize an energy-saving magnetic disk apparatus.
Generally speaking, one end of a suspension arm of a head assembly supports a slider, and the other end thereof is fastened to a spacer. The spacer is connected to an arm member which is fastened to a pivot shaft by adhesive, caulking or screws. The head assembly, the arm member and the pivot shaft form a swing arm assembly. The positioning of the head is effected by rotating this swing arm assembly by a voice coil motor.
Japanese Unexamined Patent Publication No. 2-35671 discloses a magnetic disk apparatus in which a hole is formed in the suspension arm of each head assembly and spacers and suspension arms are alternately fitted onto a shaft, the outermost suspension arms are pressed by retainers so that the suspension arms are directly joined to the shaft, thereby reducing the moment of inertia of the swing arm assembly.
Although the above-described prior-art structure can reduce the moment of inertia, it is incapable of attaining an improvement in the floating characteristics of the head, which are most important in reading and writing information. For a head to be able to levitate over the disk in a stable manner, it is necessary for the suspension arm to hold the head slider with a load of several grams. Regarding this load, only a deviation of approximately 10% from a design value is permitted. The load to be applied to the slider of the head is finely adjusted by deforming the suspension arm before the head assembly is attached to the shaft. However, when spacers are fastened to the suspension arm or when, as in the above-mentioned Japanese Unexamined Patent Publication No. 2-35671, suspension arms are held between spacers and pressurized from above and below, the condition or degree of deformation effected on the suspension arms for the purpose of fine adjustment is changed, so that the suspension arm cannot generate the predetermined loads. As a result, the designed spacing between head and disk cannot be obtained. In addition, the angle at which a slider is mounted is adversely affected with a resultant unstable floating of the head. These facts constitute an obstacle to correct writing and reading of information.